Method and apparatus for the closing by tramsverse welding of flexible tubes made of metal-thermoplastic laminate

ABSTRACT

Method and apparatus for closing by transverse welding of flexible tubes formed of a metal-thermoplastic laminate, in which the end of the flexible tube is gripped in a manner to create a transverse rectilinear closure zone, in which the zone is preheated by the application of external heat and welding is completed by induction heating.

United States Patent [191 [111 3,923,585

Vouillemin 1 Dec. 2, 1975 4] METHOD AND APPARATUS FOR THE [58] Field ofSearch 156/272, 380, 583, 498

CLOSING BY TRAMSVERSE WELDING OF FLEXIBLE TUBES MADE OF [56] ReferencesCited METAL-THERMOPLASTIC LAMINATE UNITED STATES PATENTS Inventor:Jean-Marie Vouillemin, 2,749,020 6/1956 Baxter 156/499 Ste-Menehould,France 3,326,735 6/1967 Beason Assigneez TurboPlast-Fmnce, Paris France3,632,943 l/1972 Engler et a1. 156/380 [22] Filed: Ju 1974 PrimaryExaminer-Douglas J. Drummond [21] Appl. No.: 475,425

. 7 RA Related US. Application Data [5 1 ABST 9 [62] Division of Ser. No342 689 March 19 1973 Pat Method and apparatus for closing by transverseweld- 3 837 96L ing of flexible tubes formed of a metal-thermoplasticlaminate, in which the end of-the flexible tube is [30] ForeignApplication Priority Data gripped in a manner to create a transverserectilinear closure zone, in which the zone is pre-heated by the Mar.23, 1972 France 72.10240 application of external heat and weldmg iscompleted [52 U.S. Cl 156/380; 156/498 by mducno" heatmg' [51] Int. Cl.B32B 19/02; B32B 31/00 3 Claims, 5 Drawing Figures US. Patent Dec. 2,1975 Sheet 1 of 3 3,923,585

Fig.2

US. Patent Dec. 2, 1975 Sheet 2 013 3,923,585

Fig. 4

Fig 5 METHOD AND APPARATUS FOR THE CLOSING BY TRAMSVERSE WELDING OFFLEXIBLE TUBES MADE OF METAL-THERMOPLASTIC LAMINATE This is a division,of application, Ser. No. 342,689, filed Mar. 19, 1973 now US. Pat. No.3,837,961.

This invention relates to a method and apparatus for effecting closureof flexible tubular members formed of metal-thermoplastic laminate bytransverse welding of the open end.

The invention is concerned with the field of flexible tubular members inwhich utilization is made of permanent deformation to effect thedischarge of content material.

A flexible tubular member of the type described is formed with a bodyportion of cylindrical or frustoconical configuration, the small basemounting the dispensing head while the lower end is closed after thetube has been filled.

The flexible tubular body portion is known to be formed of a laminatecomprising at least one impervious layer and two layers of thermoplasticmaterial, with the layers alternately arranged, preferably with theimpervious layer sandwiched between the layers of thermoplasticmaterial. At least one of the impervious layers is metal, such forexample as aluminum. The flexible tubular body portion is formed byoverlapping the lateral edges of the laminate to provide an outsideoverlapping portion and an inside overlapping portion which extendlongitudinally of the tubular member. Joinder of the overlappingportions is made by applying heat and pressure so that a certain portionof the thermoplastic material flows from the overlap area towards theareas immediately adjacent the overlap. This causes a reduction inthickness for the overlap area and the formation of ridges ofthermoplastic material which extend from the sections of the overlappingportion.

Transverse closure of a tubular member of the type described is madedifficult by reason of the presence of the longitudinal joint. Along theoverlapped longitudinal joint, the number of metal layers is double thatbeyond the joint, while the outer thermoplastic layers which areemployed in the transverse welding operation, although reduced inthickness, form an area of increased thickness.

Welding is effected by reducing the two contacting thermoplastic layersto the plastic state and then compressing the joint in a cold grippingmeans which causes flow of portions of thermoplastic material forautogeneous welding. This results in the formation of an external ridgealong the section external of the tubular member and an internal ridgealong the junction zone.

It is known to make the above described weld by the application ofexternal heat, i.e. heat generated outside of the joint to be formed, asby infrared radiation or by heated jaws, but the necessity to heat thethermoplastic of the internal layer to welding temperature gives rise tothe danger of overheating of the thermoplastic material in the internallayer. In addition, this procedure is slow.

It is also known to effect the weld by the use of internal heat, i.e.that which is produced in the joint to be made, as by induction heating.Under such conditions, the heat is produced in the layer or layers ofmetal which form a virtually closed circuit, but which is interrupted inline with the longitudinal joint. At that point,

there are two layers of metal separated by a thin film of thermoplasticmaterial such that the amount of heat is doubled. This causes excessiveheating of the thermoplastic material in the internal layer and leads tocarbonization thereof. In addition, in the case of a composite materialwhich is asymmetric with respect to the aluminum sheet, thethermoplastic material in the thicker external layer is only partiallyheated to the plastic stage. As a result, its outer portion remainsalmost cold while the inner portion is softened. As a result, when thetube is gripped in the cold gripping means, in the end zones which arehighly curved, the cold portion of the layer of thermoplastic materialtends to split. In contrast to the previous method, this method ofprocedure is faster and, not to say brutal.

In the French Pat. No. 1,497,846, description is made of a method forclosing by transverse welding of a flexible tube, as by longitudinalwelding of the laminate wherein the end of the tube is compressedbetween two jaws, only one of which is provided with an inductionheating means. Longitudinal welding must necessarily be in contact withthe noninductive jaw.

This method requires the longitudinal joint to be oriented with respectto the tool for making the transverse joint. This disadvantage is ofimportance when the finished tube must carry printing, an inscription ora drawing. In the case where the printing is applied after thelongitudinal weld, the tool for making the transverse weld is orientedrelative to the printing. It is impractical to orient the tool relativeboth to the printing and to the longitudinal joint.

It is an object of this invention to provide a method for closing bytransverse welding a flexible tube produced by longitudinal welding of ametal-thermoplastic laminate, the outside layers of which comprise athermoplastic material and which avoids the above mentioneddisadvantages, and it is a related object to provide an apparatus forcarrying out the same.

These and other objects of this invention will hereinafter appear andfor purposes of illustration, but not of limitation, an embodiment ofthe invention is shown in the accompanying drawings, in which FIG. 1 isa cross-sectional view of an embodiment of a laminate employed in thepractice of this invention;

FIG. 2 is a side elevational view of a flexible tube produced inaccordance with the practice of this invention;

FIG. 3 is a cross-sectional view taken along the line III in FIG. 2,showing the transverse joint for closing the flexible tube;

FIG. 4 is an elevational view showing the gripping means for flatteningthe end of the tube which is to be closed, and the pre-heating means;and

FIG. 5 is a top plan view of the induction welding means.

In accordance with the practice of this invention, the end of the tube,which is to be closed, is gripped so as to create a transverserectilinear closure zone, said zone is pre-heated by the application ofexternal heat, then the weld is completed by means of induction heating,followed by cooling of the joint produced.

The apparatus according to the invention comprises a gripping means forflattening the open part of the tube comprising two jaws of anelectrically insulating material and resistant to infra-red rays, aninduction welding means comprising two gripping means, each providedwith a cooling means and at least one of which includes an inductionmeans, and a cooling means. Upstream of the induction welding means,there is an infra-red radiation pre-heating means comprising at leastone radiating resistor, the assembly of said resistors being surroundedby a reflector for concentrating the radiation onto the end of the tubewhich projects beyond the jaws of the flattening gripping means.

The flexible tubes are formed of a metalthermoplastic laminate material,having at least one metal sheet, such as aluminum, which is sandwichedbetween two thermoplastic sheets such as of polyethylene. The laminatecan be formed of a larger number of layers, while the above-mentionedmetal sheet can be replaced for example by two metal sheets joined by athermoplastic sheet, or by a metal sheet and a paper sheet which arejoined together by way of a thermoplastic sheet.

The laminate 10, illustrated in FIG. 1, comprises an aluminum sheet 101covered on each of its faces by a layer 102 and 103 of a polyethylenecopolymer and a polyethylene layer 104 and 105. The face which isintended to form the outside surface of the tube is covered by a secondpolyethylene layer 106 having a thickness greater than that of thepreceding layer 105. The outside layer 106 can be deposited either onthe laminate before the tube is produced or on the finished tube body,before filling and closing thereof. This laminate is physicallyasymmetric relative to the metal sheet, and this is shown by anasymmetry in the transfer of heat in the welding operation. Theasymmetry is further accentuated by the poor heat conductivity ofplastic materials. This does not prevent the method of this inventionfrom achieving a perfect closure of the tube.

The flexible tube 1 1, shown in FIG. 2, is formed from such a laminate.It comprises a cylindrical or frustoconical body 111 which is producedby longitudinal welding of overlapping edge portions of the laminate toform a joint 114, which extends longitudinally through the length of thetubular member. One of the ends, the small base in the case of afrustoconical body, is provided with a dispensing head 112 which ispreferably produced by molding onto the body, while the other end issealed after filling by a transverse joint 113.

The transverse joint 113 is made by subjecting the open end bottom endportion of the tube to pressure, and heating. The material of thethermoplastic layers is softened and flows, thus forming an internalridge 117 and an extema] ridge 116 which extends towards the outside ofthe joint and which is welded to the thermoplastic layers and, inparticular, to the outside layer 106. The difficulty in this operationarises from the presence in the transverse joint 113 of an area 118which also forms part of the longitudinal joint. Although, during theformation of the longitudinal joint, the layers of thermoplasticmaterial have been reduced in thickness, their total thickness in thearea 118 remains greater than that of the adjacent layers, and there aretwo metal layers at that point instead of one. Tests, involving makingthe transverse joint by induction heating, show that with apparatuswhose current output is 3.85 KVA, the formation of a properly producedjoint, outside of the area 118 which is common to the two joints,requires a heating period of 1 second. However, it has been found thatmany welded tubes are burnt in the area 118 and that the outside layer106 has split. Burning is worse when the laminate includes a papersheet.

This disadvantage is overcome if pre-heating by infra-red radiation iseffected, by means of two resistances consuming a power of 300 watts,and positioned 6 mm from the gripped end of the tube for a period of 2seconds, followed by welding with the same induction apparatus, but fora period of only 0.6 second. A good joint is produced, without burningand without splitting the thermoplastic material. The position of thearea 118 on the transverse joint 113 can be anywhere, so that theorientation of the plane 119 of the latter need take into account onlythe position of printing on the tube body.

The apparatus shown in FIG. 4 comprises a gripping means 2 forflattening the open end of the tube 11. The gripping means 2 comprisestwo jaws 21 and 22 of an electrically insulating material which isresistant to infra-red radiation, such as those marketed under the tradenames Celoron, or Teflon (polytetrafluoroethylene). The operativesurfaces' of the jaws 21 and 22 comprise a flat portion 211 and 221respectively, parallel to the plane 119 of the joint 113, and anotherflat portion 212 and 222 respectively, which extend outwardly inopposite directions at an acute angle from the respective flat portions211 and 221. The portions 212 and 222 are symmetrical relative to theplane 119. The two jaws 21 and 22 can be opened or closed bydisplacement symmetrical relative to the plane 119 in the direction awayfrom and toward each other respectively.

The infra-red pre-heating means 3 (FIG. 4) comprises one or moreelectrical resistances 31 emitting infra-red radiation. In theembodiment illustrated, these resistances are in the form of a tube andare secured by tube-carrier clips 32 forming current connections. Areflector 33 surrounds the assembly, for concentrating the radiationonto the end of the tube 11 which projects beyond the jaws 21 and 22 ofthe gripping means 2. The means 3 is secured to a frame 34 which isadjustable in height, for example by rotation of a screw in a nut whichis secured to the frame (not shown), thereby permitting the distance ofthe tube 31 from the joint 113 to be made, to be adjusted.

The induction welding means 4 (FIG. 5) comprises two jaws 41 and 42,formed for example of a material known in the trade under the name ofAraldite. The two jaws 41 and 42 are secured to respective arms 43 and44 mounted for pivotal movement on a shaft 45 and are actuated by links46 and 47. The links 46 and 47 are pivoted on a shaft 48, controlled forexample by a pneumatic jack (not shown). The jaw 41 comprises aninsulating block molded around a hollow tubular conductor 411 formingthe induction means. A cooling means 412 such as water is circulatedthrough the conductor 411. The jaw 42 can be identical. In the preferredpractice the jaw 47 does not have any induction means but only a watercooling means 422. It thus forms an anvil jaw. The jaws come togetherwhen the jack effects downward displacement of the shaft 48 and the jawsmove apart in response to movement of the shaft in the upward oropposite direction.

Final cooling is effected by exposing the resulting.

joint to air, the gripping means 2 remaining in the clamping position.

In operation, the tube body 111, upon which is mounted the dispensinghead 112 and which has received the desired printing, is turned over sothat its open bottom end or base is directed upwardly. The substancewhich the tube is to contain is then poured therein. After orientationrelative to the printing on the tube, the open end of the tube isintroduced between the jaws 21 and 22 of the gripping means 2. The jaws21 and 22 are moved together so as to flatten the end of the tube, carebeing taken to insure that the end of the tube projects beyond the jawsby the desired amount, a little more than that required for the joint113. The end is then introduced below the pre-heating means for therequired time, for example for 2 seconds, for induction tubes with atotal power of 600 watts, positioned at 6 mm from the end of the joint113. Finally, the tube body, while still being clamped in the grippingmeans 2, is engaged between the jaws 41 and 42 in the open condition ofthe induction-welding means 4. In response toactuation of the jack tomove the shaft 48 downwardly, the jaws 41 and 42 come together, stronglyclamping the end 113 of the tube 11 between them. The induction means isthen supplied with electrical current for the desired time, for example0.6 second for a 3.85 KVA apparatus. The current is then stopped and thejaws are moved away from each other in response to raising the shaft 48as by means of the jack. It then only remains to open the gripping means2, to remove the finished tube 11.

The apparatus is normally mounted on an automatic machine comprisingmultiple working stations, the tubes passing successively from onestation to the next. The movement of the tubes can be linear orcircular, in the latter case the various stations being mounted on ahorizontal plate which rotates about a vertical axis. A machine of thistype is described in French Pat. No. 1,069,414. This described machinecomprises 11 stations, but the number of stations is here raised to 12,namely:

1. a tube-charging station;

2. a station for setting the tubes at the desired height;

3. a station for detecting the presence of a tube, this stationcomprising for example a light ray which is intercepted by the tube andwhich, if it acts on a photoelectric cell or on a photo-sensitiveresistor, blocks the following station;

4. a tube filling station;

5. a free station;

6. and 7. two infra-red radiation pre-heating stations, which compriseonly a single apparatus extending over the two stations;

8. and 9. two induction-welding stations, each station comprising aninductive gripping means (41 42);

10. and 11. two free stations, for permitting cooling of the transverseweld in free air;

12. a station for ejecting the finished tubes.

Each station can receive a plurality of tubes at once,

gripped in the same gripping means (21 22).

It will be apparent from the foregoing that there is described aninvention for closing flexible tubes of a metal-thermoplastic laminate,by means of a transverse joint, after the tubes have been filled.

It will be understood that changes may be made in the details ofarrangement and operation without departing from the spirit of theinvention, especially as defined in the following claims.

I claim:

1. Apparatus for closing the open end portion of flexible tubes formedwith a thermoplastic interlayer by transverse welding of the flexibletube comprising 1. a pair of jaws mounted for movement into and out ofgripping engagement with the opposite side of a portion of the tubeadjacent the open end to flatten and to grip the flattened end portionof the tube with a free end portion extending beyond the jaws when ingripping engagement;

2. an infrared radiation means beyond the gripping jaws for directingradiations onto the free flattened end portion of the tube extendingbeyond the jaws to pre-heat said portion, and

3. a pair of welding jaws mounted for movement into and out ofengagement with the pre-heated flattened free end portion of the tubeextending beyond the gripping jaws, at least one of said welding jawsembodying induction heating means additionally to heat the freeflattened end portion of the tube extending beyond the gripping jaws andto weld the same when in position of engagement with the tube, saidwelding jaws also embodying cooling means for setting the weld.

2. Apparatus as claimed in claim 1 which includes reflector means forconcentrating the radiations onto the flattened end portion of the tubeextending beyond the gripping means.

3. Apparatus as claimed in claim 1 in which the infrared radiation meanscomprises at least one radiating electrical resistance means and whichincludes a reflector surrounding resistance means for concentrating theradiations onto the end of the tube which projects beyond the grippingmeans.

1. APPARATUS FOR CLOSING THE OPEN END PORTION OF FLEXIBLE TUBES FORMEDWITH A THERMOPLASTIC INTERLAYER BY TRANSVERSE WELDING OF THE FLEXIBLETUBE COMPRISING
 1. A PAIR OF JAWS MOUNTED FOR MOVEMENT INTO AND OUT OFGRIPPING ENGAGEMENT WITH THE OPPOSITE SIDE OF A PORTION OF THE TUBEADJACENT THE OPEN END TO FLATTEN AND TO GRIP THE FLATTENED END PORTIONOF THE TUBE WITH A FREE END PORTION EXTENDING BEYOND THE JAWS WHEN INGRIPPING ENGAGEMENT;
 2. AN INFRARED RADIATION MEANS BEYOND THE GRIPPINGJAWS FOR DIRECTING RADIATIONS ONTO THE FREE FLATTENED END PORTION OF THETUBE EXTENDING BEYOND THE JAWS TO PRE-HEAT SAID PORTION, AND 2.Apparatus as claimed in claim 1 which includes reflector means forconcentrating the radiations onto the flattened end portion of the tubeextending beyond the gripping means.
 2. an infrared radiation meansbeyond the gripping jaws for directing radiations onto the freeflattened end portion of the tube extending beyond the jaws to pre-heatsaid portion, and
 3. A PAIR OF WELDING JAWS MOUNTED FOR MOVEMENT INTOAND OUT OF ENGAGEMENT WITH THE PRE-HEATED FLATTENED FREE END PORTION OFTHE TUBE EXTENDING BEYOND THE GRIPPING JAWS, AT LEAST ONE OF SAIDWELDING JAWS EMBODYING INDUCTION HEATING MEANS ADDITIONALLY TO HEAT THEFREE FLATTENED END PORTION OF THE TUBE EXTENDING BEYOND THE GRIPPINGJAWS AND TO WELD THE SAME WHEN IN POSITION OF ENGAGEMENT WITH THE TUBE,SAID WELDING JAWS ALSO EMBODYING COOLING MEANS FOR SETTING THE WELD. 3.a pair of welding jaws mounted for movement into and out of engagementwith the pre-heated flattened free end portion of the tube extendingbeyond the gripping jaws, at least one of said welding jaws embodyinginduction heating means additionally to heat the free flattened endportion of the tube extending beyond the gripping jaws and to weld thesame when in position of engagement with the tube, said welding jawsalso embodying cooling means for setting the weld.
 3. Apparatus asclaimed in claim 1 in which the infra-red radiation means comprises atleast one radiating electrical resistance means and which includes areflector surrounding resistance means for concentrating the radiationsonto the end of the tube which projects beyond the gripping means.